Did ‘Twilight’ Star Kristen Stewart Cheat on Robert Pattinson With Her ‘Snow White and the Huntsman’ Director?

Several media reports indicate the pairing between Robert Pattinson and Kristen Stewart, stars of the popular ‘Twilight’ movie franchise and allegedly an off-screen couple, as well, could be on the rocks after Stewart reportedly had a fling with a married movie director.

Seems Stewart, 22, recently had what’s described as a “marathon make-out session” with her ‘Snow White and the Huntsman’ director Rupert Sanders, who’s almost twice her age and married with two kids — and Us Magazine claims to have photographic evidence of the tryst.

I’m deeply sorry for the hurt and embarrassment I’ve caused to those close to me and everyone this has affected. This momentary indiscretion has jeopardized the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I’m so sorry.”

Adding to an already icky situation? Sanders’ wife is actress Liberty Ross, who played Stewart’s mother in the ‘Snow White’ movie.

“[Kristen] wasn’t having an affair with Rupert. It was just a fleeting moment that shouldn’t have happened,” a source says. “She never meant to hurt anyone. She’s a good person who just made a bad choice.”

Stewart and Pattinson, 26, met on the set of the first ‘Twilight’ movie and became a couple soon after. And as recently as Sunday, when they attended the Teen Choice Awards together, all seemed well. But then the story of Stewart’s supposed infidelity surfaced.

“Kristen is absolutely devastated,” says the insider. “[The fling] was a mistake and a complete lapse in judgment.”

Reps for the parties involved haven’t responded to requests for comment, but Sanders’ wife did post a one-word tweet on her now-deleted Twitter account just before news of the cheating scandal broke: “Wow.”